1. Field of the Invention
The present invention relates to electrostatic discharge protection devices, and in particular relates to electrostatic discharge protection devices with multiple discharging paths.
2. Description of the Related Art
An electrostatic discharge (ESD) event happens when electrostatic charges move from one surface to another. In VLSI circuits, electrostatic current may cause damage to semiconductor junction, metal part, and gate structure. One of the most widely used ESD protection devices is silicon controlled rectifier (SCR). FIG. 1 shows a silicon controlled rectifier 10, comprising a first BJT QPNP and a second BJT QNPN. The emitter of the first BJT QPNP is electrically connected to an input/output terminal I/O of a circuit under protection. The base of the first BJT QPNP is connected to the collector of the second BJT QNPN. The base of the second BJT QNPN is connected to the collector of the first BJT QPNP. The emitter of the second BJT QNPN is electrically connected to a reference voltage node GND. When an electrostatic discharge (ESD) event occurs at the input/output terminal I/O, a high voltage potential sets the first BJT QPNP to a forward biased state, and subsequently sets the second BJT QNPN to a forward biased state, creating a current path to dissipate electrostatic charges from the input/output terminal I/O to the reference voltage node GND.
However, ESD efficiency of SCR devices may be adversely affected by smaller electrostatic current flow paths. A novel ESD protection device with larger current capacity is desired.